Three
Sida spp.
viz. S. acuta,
S. rhombifolia var.
rhomboidea,
S. cordata and a putative hybrid between
S. acuta and
S. rhombifolia var.
rhomboidea were cytogenetically investigated to elucidate their characteristic karyotypes.
S. acuta and
S. rhombifolia var.
rhomboidea possessed 2
n=28 and 2
n=14 chromosomes, respectively. In
S. cordata, 2
n=32 and in the putative hybrid, 2
n=28 chromosomes were observed. The total length of 2
n chromosome complements in
S. acuta and
S. rhombifolia var.
rhomboidea were 55.6 μm, and 35.7 μm, respectively. In
S. cordata, total length of 2
n chromosome complement was 47.4 μm and in the putative hybrid, 96.7 μm. Except the putative hybrid, all species had only metacentric chromosomes. On the other hand, the putative hybrid had 6 sub-metacentric (6 sm) and 22 metacentric (22 m) chromosomes. Four CMA-positive bands were found in
S. acuta,
S. cordata and the putative hybrid, whereas, 2 such bands occurred in
S. rhombifolia var.
rhomboidea. These banded regions were DAPI-negative, indicating their absolute GC-rich nature. Both DAPI-positive (9) and negative (4) bands were found in
S. cordata. An analysis of these data indicates that each
Sida species possesses a distinct karyotype. The different 2
n chromosome number, centromeric formula, length of total chromosome complements and fluorescent banding pattern unequivocally indicate a separate taxonomic rank of the putative hybrid.
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